B01D53/9459—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts

B01D53/9463—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts with catalysts positioned on one brick

B01D53/9468—Removing one or more of nitrogen oxides, carbon monoxide, or hydrocarbons by multiple successive catalytic functions; systems with more than one different function, e.g. zone coated catalysts with catalysts positioned on one brick in different layers

B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00

B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals

B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36

F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust

F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters

F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices

F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors, e.g. catalysed diesel particulate filters

F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents

F01N3/0821—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with particulate filters

F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents

F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances

F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents

F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances

F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust

F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control

F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters

F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES

F01N2240/00—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being

F01N2240/25—Combination or association of two or more different exhaust treating devices, or of at least one such device with an auxiliary device, not covered by indexing codes F01N2230/00 or F01N2250/00, one of the devices being an ammonia generator

F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES

F01N2610/00—Adding substances to exhaust gases

F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea

Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE

Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE

Description

The invention relates to a catalytically activated diesel particulate filter, in addition to the typical properties of a diesel particulate filter comprising an ammonia-blocking effect. The invention further relates to exhaust gas purification systems for removing nitrogen oxides and particulates from the exhaust gas of lean operating internal combustion engines using the catalytically activated diesel particulate filter according to the invention in various embodiments.

The emissions contained in the exhaust gas of a motor vehicle can be divided into two groups. Thus, the term primary emission pollutant gases that are directly caused by the combustion process of the fuel in the engine and are present in the so-called untreated emissions even before the passage of waste gas cleaning devices. As a secondary emission such harmful gases are called, which may arise as by-products in the emission control system.

The exhaust gas from lean burn engines contains a relatively high oxygen content of up to 15 vol .-% the usual primary emissions of carbon monoxide CO, hydrocarbons HC and nitrogen oxides NOx. In the case of diesel engines still comes to gaseous emissions add a primary particle emission, which mainly consists of soot residues and optionally organic agglomerates and resulting from partially incomplete fuel combustion in the cylinder.

Compliance with the emission limits prescribed by the future exhaust emission legislation in Europe, North America and Japan, in particular, requires in the case of diesel vehicles in addition to a nitrogen oxide removal from the exhaust gas ( "denitrification") and its purification of particles. The harmful gases carbon monoxide and hydrocarbons may be prepared from the lean exhaust gas by oxidation of a suitable oxidation catalyst easily be made unharmful. the reduction of the nitrogen oxides to nitrogen is much more difficult because of the high oxygen content. the use of special diesel particulate filter is indispensable for the removal of particulate emissions. Known methods for removing nitrogen oxides from exhaust gases are for a method using nitrogen oxide storage catalysts (NOx storage Catalyst NSC) and on the other process for the selective catalytic reduction (selective catalytic reduction SCR) by ammonia in a suitable Kataly sator, SCR catalyst for short.

The cleaning effect of nitrogen oxide storage catalysts is because the nitrogen oxides from the storage material of the storage catalyst, predominantly in the form of nitrates stored in a lean operating phase of the motor. If the storage capacity of NSC exhausted, the catalyst must be regenerated in a subsequent rich operating phase of the engine. That is, the nitrates formed beforehand decomposed and again released nitrogen oxides are reacted with the reducing exhaust gas portions on the storage catalyst to nitrogen, carbon dioxide and water. The operation of nitrogen oxide storage catalysts is described in detail in the SAE document SAE 950,809th

Since the realization of a rich operating phase in diesel engines is not readily possible and the adjustment of the required for regeneration of the NSC rich exhaust gas conditions often requires assistance as a post fuel injection in the exhaust system, for removing nitrogen from diesel vehicle exhaust gas is preferably used, the SCR method.

In this case, depending on the engine design and construction of the exhaust system, a distinction between "active" and "passive" SCR process, said to be used as a reducing agent for denitration in "passive" SCR process in the exhaust system selectively generated ammonia secondary emissions.

For example, US describes 6,345,496 Bl a process for the purification of engine exhaust gas, wherein alternately repeated lean and rich air / fuel ratios are set and the exhaust gas thus generated is passed through an exhaust system, the upstream contains a catalyst containing only under rich exhaust gas conditions NO x reacting NH 3, while the outflow side, another catalyst is arranged, the x adsorbed in the lean exhaust gas NO or einspeichert, this releases the fat, so that it can react to form nitrogen generated from the upstream catalyst NH 3. As an alternative, according to US 6,345,496 Bl, a NH 3 -adsorption and oxidation catalyst be disposed on the outflow side which stores the rich NH 3 desorbed this in the lean and oxidized with oxygen to nitrogen and water. Further disclosures of such processes are known.

As stated, the use of nitrogen oxide storage catalysts have such "passive" SCR processes have the disadvantage that one of its major components is the provision of a rich exhaust gas conditions which are generally required for the in situ generation of ammonia as a reducing agent.

In contrast, the reducing agent from an entrained auxiliary tank metered into "active" SCR process using an injection nozzle into the exhaust line. Can also be used a readily decomposable to ammonia, such as urea or ammonium carbamate except ammonia as such. Ammonia must the exhaust gas at least in the stoichiometric ratio to the nitrogen oxides are fed. the exact dosage of ammonia presents great difficulties because of the strongly fluctuating operating conditions of the motor vehicles. In part, this leads to considerable ammonia breakthroughs downstream of the SCR catalyst. to avoid ammonia secondary emission is usually behind the SCR catalytic converter arranged an oxidation catalyst prepared by breaking ammonia will oxidize to nitrogen. such a catalyst is referred to as ammonia slip catalyst.

Ammonia slip catalysts which are arranged for the oxidation of ammonia which breaks through behind a SCR catalyst are, in various exemplary forms are known. For example, DE 3929297 C2 (US 5,120,695) describes such a catalyst assembly. Accordingly, the oxidation catalyst is applied as a coating on a downstream portion of the integral reduction catalyst designed as an unsupported extrudate in honeycomb form, wherein the coated region with the oxidation catalyst makes up 20 to 50% of the total catalyst volume. The oxidation catalyst contains, as catalytically active component at least one of the platinum group metals platinum, palladium and rhodium deposited on cerium oxide, zirconium oxide and aluminum oxide as support materials. According to EP 1399246 Bl, the platinum group metals may also be applied directly on the components of the reduction catalyst as support materials by impregnating with soluble precursors of the platinum group metals.

According to JP 2005-238199, the noble metal-containing layer of an ammonia oxidation catalyst can also be introduced under a coating of titanium oxide, zirconium oxide, silicon oxide or aluminum oxide and a transition metal or a rare-earth metal.

For the removal of particulate emissions from the exhaust gas of diesel vehicles, special Diesel particulate filters are used which may be provided to improve their properties having an oxidation catalyst-containing coating. Such a coating is used, as described in the SAE document SAE 2005-01-1756 detail of lowering the activation energy for the oxygen-based particulate burnoff (soot combustion) and hence the lowering of the soot ignition temperature on the filter, improving the passive regeneration behavior by oxidation of the exhaust enhaltenen nitric oxide to nitrogen dioxide and suppression of breakthroughs of hydrocarbon and carbon monoxide emissions.

A particular problem in the coating of filter substrates, the increase in the exhaust back pressure by the applied coating. The exhaust gas pressure is increased already by the soot deposits on the filter during operation continuously and thus reduces the performance of the engine. The filter must therefore be regenerated from time to time by burning off the soot. If it is a coated filter substrate, the soot combustion is indeed usually relieved, but the exhaust back pressure of the blank, coated filter is already often already higher than that of an uncoated filter. It is therefore not readily possible to change the catalytic functionality of a particulate filter by changes in the coating, for example by introducing additional catalytically active components.

Is now required with the aim of fulfilling statutory exhaust emission limits both the denitrification as well as the removal of particles from the exhaust gas of diesel vehicles, so combining the measures described for removing individual pollutant gases in a corresponding conventional exhaust system by a series connection. For example, WO 99/39809 describes an exhaust gas purification system in which an oxidation catalyst for oxidising NO to NO x to NO 2 to follow, a particulate filter, a metering device for a reducing agent and an SCR catalyst with each other. To prevent ammonia breakthroughs by the SCR catalyst is usually an additional ammonia slip catalyst is still required, which continues the series of catalysts downstream of the SCR catalytic converter.

DE 20 2005 008 146 Ul discloses an exhaust system for a motor vehicle comprising at least one regenerable particle filter and a particulate filter downstream of the SCR catalyst with ammonia storage capacity, the downstream SCR catalytic converter, the information in this according to type serves especially during the regeneration of the particulate filter occurring NH 3 spikes trap in the exhaust gas, so the SCR catalyst is arranged downstream of the particulate filter.

Such conventional systems because of the multitude of catalysts required expensive. The series connection of the catalysts also leads to a high demand for space in the exhaust system. Your accommodation designed often difficult, particularly in smaller vehicles. In addition, the series connection of catalysts, each of which carries its own back pressure on the gas to be cleaned to unfavorable values ​​of the exhaust gas back pressure over the whole exhaust system and thus reduces the performance of the engine. Performs

In a preferred embodiment of the system 20205008146 Ul described in the DE of the particulate filter and the SCR catalyst form a common, combined unit with a common insert body, which is typically a monolithic ceramic substrate ULTRASONIC. The SCR catalyst is formed only by a corresponding coating of the ceramic substrate on the downstream side.

It is an object of the present invention, existing by Verbeserung

to provide particulate filter technology components available through their use

can be simplified exhaust gas purification systems for simultaneous denitrification and removal of particles from the exhaust gas of lean-burn engines with a saving in exhaust gas purification units. At the same time, the object of the present invention to contribute to minimizing the exhaust back pressure of such investments and pinpoint potential for cost savings.

This object is achieved by a catalytically activated diesel particulate filter comprising a filter body and an oxidation-active catalytic coating, and a further catalytically active in the SCR reaction coating. The catalytically active in the SCR reaction coating is characterized in that therein an ammonia storage material is contained. The diesel particulate filter is characterized in that an arrangement of the layers is maintained such that the gas to be cleaned first passes through the catalytically active in the SCR reaction and subsequently coating the oxidation-active catalytic coating.

The object is further solved by an exhaust gas purification system for removing nitrogen oxides and particulates from the exhaust gas of lean operating internal combustion engines which contains an inventive catalytically activated diesel particulate filter in addition to a suitable catalyst for removing nitrogen oxides.

By combining the already optionally contains to in conventional particle filters oxidation-active coating having a in the SCR reaction catalytically active coating ( "SCR coating"; "SCR-active layer"), the diesel particulate filter includes an additional ammonia barrier effect. The combination of the coatings enables the particulate filter, in addition to the already existing functions (particle filtering / particulate burnoff with lowered soot ignition temperature, improved passive regeneration behavior, NO oxidation, suppression of breakthroughs of CO and HC emissions) to reduce, on the one hand the nitrogen oxides to nitrogen and on the other hand to oxidize ammonia to nitrogen. the gas to be cleaned first passes through the SCR-active layer and then the oxidation-active coating, the multifunctionality is based in terms of conversion of the nitrogen-containing pollutant gases presumably due to the following, a schematically illustrated in Figure 1 reaction sequence: 1) nitrogen oxides and ammonia from the exhaust gas to the SCR-active layer (1) absorbed and react in a selective catalytic reaction to form water and nitrogen which desorb after reaction completion. Ammonia is present in überstöchiometri shear quantity, that is present in excess.

3) Not stored ammonia passes through the SCR-active layer (1) through the oxidation-active coating (2). Here, nitrogen and nitrogen oxides are generated. The resulting nitrogen diffuses unchanged through the

SCR-active layer (1) therethrough and into the atmosphere.

4) Before the (in the oxidation-active layer 2) formed nitrogen oxides leave the system, they pass through the SCR-active coating (1) again. Here they are with previously stored ammonia NH 3 _ STO r ed reacted in an SCR reaction to N 2.

Thus, the reaction process described leads to the highest possible conversions of the nitrogen-containing pollutant gases, it is advantageous if the SCR-active coating has sufficient ammonia storage capacity. To ensure this, the SCR-active layer in the inventive diesel particulate filter includes an ammonia storage material. Ammonia storage materials as referred to herein are compounds which contain acidic centers at which ammonia can be bound. The skilled artisan distinguishes this in Lewis acid sites for the physisorption of ammonia and Bronsted acid sites for the chemisorption of ammonia. An ammonia storage material in a diesel particulate filter according to the invention must contain a significant proportion of Bronsted acidic sites, and optionally Lewis acid sites to ensure sufficient ammonia storage capacity.

What is the ammonia storage capacity of a catalytic material, can be determined by means of the temperature programmed desorption. In this standard method for characterizing the catalysts of heterogeneous material to be characterized is loaded after baking of optionally adsorbed components such as water with a defined amount of ammonia gas. This is done at room temperature. Then, the sample is heated under inert gas at a constant heating rate, so that previously recorded from the sample ammonia gas is desorbed and can be determined quantitatively with a suitable analysis. As a parameter for the ammonia storage capacity of the material an amount of ammonia is obtained in milliliters per gram of catalyst material, always, the term "catalyst material", the material used for characterization. This parameter is dependent on the chosen heating rate. In this document, specified values ​​always relate on measurements with a heating rate of 4 Kelvin per minute.

The ammonia storage capacity of the SCR reaction catalytically active coating in the inventive diesel particulate filter is preferably at least 20 milliliters of ammonia per gram of catalyst material, more preferably up to 70 milliliters per gram of catalyst material. Particularly well suited to SCR-active layers having an ammonia storage capacity of 25 to 40 milliliters of ammonia per gram of catalyst material.

SCR-active coatings with the described ammonia storage properties preferably comprise zeolites with hydrogen cations ( "H-zeolite") or transition metal cations have been exchanged. Good suitable exchanged with iron or copper or iron and copper zeolites, which are preferably beta- zeolite or Y-zeolite or faujasite or mordenite or ZSM-5 or combinations thereof.

In particularly suitable embodiments of the invention, the SCR-active coating in the inventive diesel particulate filter is free of precious metals. This ensures that the selectivity in the SCR reaction is as high as possible. To further improve the SCR type additives may also selected from the group consisting of cerium oxide, titanium oxide, zirconium oxide, vanadium oxide, molybdenum oxide, tungsten oxide, silica, and mixtures and / or composite oxides thereof may be present. Many conventional diesel particulate filter containing an oxidation-active coating. In the inventive diesel particulate filter, this is preferably free of zeolites. In particularly suitable embodiments of the invention, the oxidation-active catalytic coating comprises platinum or palladium or mixtures thereof on a support material selected from the group consisting of hochoberflächigem, active alumina, cerium oxide, zirconium oxide, titanium oxide, silicon oxide and mixtures or mixed oxides thereof.

The oxidation-active catalytic coating, and the catalytically active in the SCR reaction coating be applied in a defined manner to a suitable for the deposition of diesel particulate filter body. Suitable filter body are selected from the group of the ceramic wall flow filter substrates, the sintered metal filter bodies or the ceramic or metallic foam structures. ceramic wall flow filter substrates, the walls are preferably used have with an open-pore structure with a porosity of 40 to 80% and an average pore diameter from 9 to 30 micrometers. ceramic wall flow filter substrates having a porosity of 45 to 65% and an average pore diameter of 9-22 micrometers are particularly preferably used.

In the application of the coatings on the filter body on the one hand to ensure that the time required for the described reaction mechanism arrangement of the layers is maintained such that the gas to be cleaned first, the catalytically active in the SCR reaction coating, and subsequently through the oxidation-active catalytic coating happens. Furthermore, the possibility of back diffusion of the exhaust gas from the oxidation-active coating by the SCR-active coating must be added to the gas space. On the other hand, to ensure that the dynamic pressure characteristics are not substantially deteriorated the resulting catalytically activated diesel particulate filter. This sum of the requirements is a challenge in the production of catalytically activated diesel particulate filter according to the invention.

Regardless of the type of the filter body used in the oxidation-active catalytic coating (2) is first applied to the support body serving as a filter body (3), wherein it occupies the entire length of the component. The resulting oxidation-coated filter then represents the carrier body for catalytically active in the SCR reaction coating (1). Thus, the SCR-active coating is applied to the oxidation-active coating. In the preferred embodiment, the SCR-active coating occupies only a part of the length of the component and is arranged on the upstream side, as shown in FIG. 2 The direction of flow of the exhaust gas is indicated by an arrow. By this arrangement, the gas to be cleaned according to the requirements of the assumed reaction mechanism first comes with the SCR-active coating in contact before it can be implemented on the oxidation-active coating. Also, the back diffusion of the exhaust gas through the SCR-active coating in the gas space, the close contact of the two layers is a prerequisite is secured. Moreover, by reducing the SCR-active coating on a portion of the length of the component

a) ensure the minimization of the back pressure of the component and

b) ensures that the advantageous for a catalytically coated diesel particulate filter properties as the particulate burnoff at reduced soot ignition temperature, the improved passive regeneration behavior and the suppression of breakthroughs of CO and HC emissions are maintained.

The question is to occupy the SCR-active coating which portion of the length of the component is dependent on the mass flow of the exhaust gas to be purified and the concentration of the nitrogen-containing pollutant gases contained therein. It is to be dimensioned such that occurring ammonia openings can be completely converted to nitrogen. Preferably, the active in the SCR reaction catalytic coating takes 5 to 50% of the length of the component a, particularly preferably 10 to 30%.

In the preferred embodiments of the invention, a wall flow filter substrate is used. To minimize the back pressure of the catalytically activated diesel particulate filter according to the invention the oxidation-active catalytic coating is introduced over the entire length of the component into the pores of the walls of the ceramic wall flow filter substrate, so that it is distributed homogeneously in the particular wall of the wall flow filter substrate. As this coating is by feeders, 10 2004 040 548 Al the applicant is described for example in DE.

Figures 3 and 4 show particularly preferred coating arrangements in catalytically activated Wandflußfiltersubstraten as sections of the structure each with an inflow passage (4) and a discharge channel (5). The direction of flow of the exhaust gas is indicated by arrows. Arrival and discharge channel are closed by a permeable for the exhaust wall (3a) with an open-pored structure and separated from each other for removal or upstream side by a gas-tight closure channel (3b).

The embodiment of the catalytically activated diesel particulate filter according to the invention shown in Figure 3 is preferably selected when a conventional oxidation-active coating containing wall flow filter substrate without losing its previous characteristics to be extended by an ammonia blocking function. Such conventional, catalytically activated wall flow filter substrates often have a homogeneously distributed in the wall, oxidation-active coating over the entire length of the component, which fills the pores up to the inflow-side surface. To generate the ammonia-blocking function, a catalytically active in the SCR reaction coating is applied over part of the length of the component to such a particulate filter on the upstream side. Preferably, the SCR-active layer on the upstream surface of the wall is arranged and takes up 5 to 50% of the length of the component, particularly preferably 10 to 30%.

The embodiment illustrated in Figure 4 is particularly preferred when the inventive catalytically activated Dieselpartikelfϊlter is used in an exhaust gas purification system, on the one hand dispose with a inflow side upstream highly active oxidation function for elimination of CO and HC breakthroughs in the other hand, increased demand for the denitrification of exhaust gas there is, provided a diesel particulate filter according to the invention is therein generally exposed to exhaust gas with temperatures in the range of 100 to 250 ° C. In this embodiment, both the oxidation-active coating and the SCR-active coating over the entire length of the component are distributed homogeneously in the wall, wherein the SCR-active coating fills the pores up to the inflow-side surface of the wall, while the oxidation-active coating, the pores up fills toward the downstream surface of the wall. also all this arrangement satisfied by the reaction mechanism adopted and the required back pressure characteristics existing requirements. The arrangement of the SCR-active coating over the entire length of the component, the catalytically activated diesel particulate filter in this way not only shows an ammonia barrier function, but in addition a complete low-temperature SCR activity.

Through the use of catalytically activated Dieselpartkelfilters conventional exhaust gas purification systems according to the invention for removing nitrogen oxides and particulates from the exhaust gas of lean operating internal combustion engines can be greatly simplified. Figure 5 shows an exemplary exhaust system according to the prior art, as described in WO 99/39809, in the embodiment as a double-flow system. It is followed by each cylinder bank of the engine (0), an exhaust system part to which a diesel oxidation catalyst (6; 6 ') includes. After merging, the exhaust lines in succession an optionally catalytically activated diesel particulate filter (7), a metering device for the required in the SCR reaction the reducing agent (8), such as urea and an SCR catalyst (9) is arranged in the flow direction. To prevent ammonia breakthroughs, a downstream ammonia barrier catalyst (10) is required.

By using the inventive component the essential elements of such an exhaust gas purification system can be reduced. For removing nitrogen oxides and particulates from the exhaust gas of lean operating internal combustion engines now it is sufficient if a corresponding plant contains a suitable catalyst for removing nitrogen oxides and a catalytically activated diesel particulate filter according to the invention. In the SITUATE RECORDER catalyst for removing nitrogen oxides can be, disposed on the upstream side of a diesel particulate filter according to the invention (11), nitrogen oxide storage catalytic converter (12, 12 '). Such an embodiment is schematically illustrated for the case of a double-flow configuration of the system in FIG. 6

In a preferred form of the exhaust system according to the invention, an SCR catalyst (9) is used as the denitration catalyst with a suitable means for

Dosage of ammonia or an ammonia to zersetzlichenVerbindung (8) used, which is also located on the upstream side of the diesel particulate filter according to the invention (11). Such an embodiment is illustrated for the case of a double-flow configuration of the system shown schematically in FIG. 7 It may be for use in some types of vehicles advantageous if in the emission control system between the predominantly lean-operated internal combustion engine (0) and the means for metering ammonia or a compound decomposable to ammonia (8) a diesel oxidation catalyst (6, 6 ') or a three-way catalyst (13, 13 ') or a nitrogen oxide storage catalyst (12,12') or combinations thereof are arranged.

The following figures and examples are intended to illustrate the invention.

Figure 1; Operating principle of the diesel particulate filter according to the invention in the implementation of nitrogen-containing pollutant gases.

2 shows arrangement of the SCR-active coating (1) and the oxidation-active coating (2) on a serving as the support body filter body (3) in a present invention, catalytically activated diesel particulate filter.

Figure 4: Preferred arrangement of the coatings in an inventive catalytically active wall flow filter substrate, are distributed in the both coatings homogeneously in the wall (3a), wherein the SCR-active coating (1) fills the wall (3a) to the inflow duct (4) towards, while the oxidation-active coating (2), the wall (3a) to the discharge channel (5) towards fills; (3b) denotes the respective gas-tight channel degrees.

Figure 5; Exhaust gas purification system for removing nitrogen oxides and particulates from the exhaust gas of lean operating internal combustion engines (0) according to the prior art in a two-flow execution that a diesel oxidation catalyst (6, 6 '), an optionally catalytically activated diesel particulate filter (7), a metering device for the required in the SCR reaction the reducing agent (8), such as urea, a SCR catalytic converter (9) and a downstream ammonia barrier catalyst (10).

Figure 6: Inventive exhaust gas purification system for removing nitrogen oxides and particulates from the exhaust gas of lean operating internal combustion engines (0) in two-flow configuration that an inventive catalytically activated diesel particulate filter (11) and the inflow side a

Nitrogen oxide storage catalytic converter (12, 12 ') contains.

Figure 7; Exhaust gas purification system according to the invention for removing nitrogen oxides and particulates from the exhaust gas of lean operating internal combustion engines (0) in two-flow configuration having a Inventions according catalytically aktivertes diesel particulate filter (11) and the inflow side, an SCR catalyst (9) provided with means for metering ammonia or to ammonia zersetzlichenVerbindung (8). Optionally, between the motor (0) and metering device (8) is a diesel oxidation catalyst (6, 6 ') and / or a nitric oxide Speicherkata- lyst (12, 12') and / or a three-way catalyst (13, 13 ') may be disposed.

Figure 8: activity in the oxidation of ammonia, measured on a provided with an oxidation-active coating wall flow filter substrate according to the prior art ([# 0], 0), and two inventive catalytically activated diesel particulate filter with an oxidation-active and an SCR active coating. The diesel particulate filter according to the invention [# 1] (•) in the SCR-active coating an iron-exchanged zeolite, a diesel particulate filter [# 2] according to the invention (A) a copper-exchanged zeolite. 9 shows selectivity to nitrogen in ammonia oxidation, measured on a provided with an oxidation-active coating wall flow filter substrate according to the prior art ([# 0], 0), and two inventive catalytically activated diesel particulate filter with an oxidation-active and an SCR active coating. The diesel particulate filter according to the invention [# 1] (•) in the SCR-active coating an iron-exchanged zeolite, a diesel particulate filter [# 2] according to the invention (A) a copper-exchanged zeolite.

In the examples described below, various embodiments of the catalytically activated diesel particulate filter according to the invention were prepared. Their reactivity and selectivity in the ammonia oxidation was studied in comparison to the produced in Comparative Example conventional diesel particulate filter on a model gas unit. The following test conditions were selected:

By means of a suitable gas analysis, the concentrations of ammonia, nitrous oxide, nitrogen monoxide and nitrogen were detected after catalyst. Under the reasonable assumption that in addition to these nitrogen-containing gases and molecular nitrogen no further nitrogen-containing reaction products are formed from the ammonia-oxidation, the concentration of the reaction the target product N 2 can be determined from the following balance equation:

From the thus obtained nitrogen concentration and the ammonia concentration metered, selectivity is calculated to nitrogen as follows:

S N Y%] = - - ^ 100

To evaluate the measurement results, the concentration of ammonia on the catalyst and the selectivity were applied to nitrogen as a function of temperature. The results are shown in FIGS. 8 and 9

Comparative Example:

A wall flow filter substrate of silicon carbide has been provided with a conventional oxidation-active coating, which has been introduced using the procedure described in DE 10 2004 040 548 Al in the wall.

The filter substrate having a diameter of 14.4 centimeters, a length of 7.62 centimeters, and had 47 cells per square centimeter with wall thickness of 0.3 millimeters. The walls of the filter substrate shown pores with an average diameter of 20 micrometers, the porosity of the walls was 60%.

The oxidation-active coating contained substantially platinum doped with lanthanum oxide on a high surface area alumina was supported. The amount of coating applied was chosen so that the finished diesel particulate filter contained 0.7 g / L of noble metal based on the volume of the coated filter substrate. three cores were taken with a diameter of 2.54 centimeters from the finished diesel particulate filter. On one of these cores [# 0], the characteristic ammonia oxidation behavior was studied according to the method described above in a model gas unit.

Example 1:

A second core, which had been taken from the diesel particulate filter of Comparative Example was on the upstream side, an active in the SCR reaction coating containing primarily iron-exchanged zeolites, applied. The length of the coated area was 2.54 centimeters, ie 33% of the length of the overall component. There were 50 g / L of the SCR-active material based on the volume of the filter substrate, is applied.

The characteristic ammonia oxidation behavior of the catalytically activated diesel particulate filter according to the invention [# 1] thus obtained was investigated in the model gas system according to the procedure described above.

Example 2:

To the third core, which had been taken from the diesel particulate filter of Comparative Example was on the upstream side, an active in the SCR reaction coating containing predominantly copper-exchanged zeolites, applied. The length of the coated area was 2.54 centimeters, ie 33% of the length of the overall component. There were 50 g / L of the SCR-active material based on the volume of the filter substrate, is applied.

Also, the characteristic ammonia oxidation behavior of this catalytically activated diesel particulate filter [# 2] according to the invention was investigated in the model gas system according to the procedure described above.

Figures 8 and 9 show the result of the investigations in the model gas.

In Figure 8, the ammonia concentration is plotted as a function of reaction temperature on the catalyst. This information serves as a measure for the general activity of the investigated diesel particulate filter in the ammonia oxidation. It is obvious that diesel particulate filter according to the invention in its general ammonia oxidation not tion activity differ significantly from the conventional diesel particulate filter: Above 250 0 C is oxidized ammonia completely.

The main advantage of catalytically activated diesel particulate filter according to the invention is reflected in the selectivity of the ammonia oxidation to nitrogen. During this the conventional diesel particulate filter (0) is lost above 300 0 C, since ammonia completely to nitrogen oxides (mainly NO 2) is over-oxidized, show diesel particulate filter according to the invention over the entire temperature range excellent selectivity data. The best results with selectivity values ​​of over 70% are used for the diesel particulate filter [# 2] (A) observed with the copper-containing, SCR-active coating, but also shows diesel particulate filter according to the invention [# 1] (•) with the iron-containing SCR-active coating in the temperature range 250 to 550 0 C with good selectivity values over 30%.

Thus, catalytically activated diesel particulate filter according to the invention are suitable with ammonia barrier effect excellent for use in exhaust systems that serve the simultaneous removal of nitrogen-containing pollutant gases and particles, and which may now be in the described manner according to the invention simplified.

Claims

claims

1. Catalyst comprising contains activated diesel particulate filter a filter body and an oxidation-active catalytic coating, and a further catalytically active in the SCR reaction coating in which an ammonia storage material is contained, d ad urch ge ke nnze i ch n et that arrangement of the layers is maintained such that the gas to be cleaned first passes through the catalytically active in the SCR reaction and subsequently coating the oxidation-active catalytic coating.

3. Catalytically activated diesel particulate filter according to claim 2, characterized geke n nze i ch n et that the catalytically active in the SCR reaction comprises one or more coating exchanged with Wasserstofϊkationen or transition metal cations zeolites.

4. Catalytically activated diesel particulate filter according to claim 3, characterized geke nnze i chn et that the catalytically active in the SCR reaction comprises one or more coating exchanged with iron or copper or iron and copper zeolites.

6. Catalytically activated diesel particulate filter according to claim 3, characterized in that the catalytically active in the SCR reaction is free of precious metals coating.

7. Catalytically activated diesel particulate filter according to claim 1, characterized in that the oxidation-active catalytic coating is free of zeolites.

8. catalytically active diesel particulate filter according to claim 7, characterized in that the oxidation-active catalytic coating of platinum or palladium or

Mixtures thereof on a support material selected from the group consisting of hochoberflächigem, active alumina, cerium oxide, zirconium oxide, titanium oxide, silicon oxide and mixtures or mixed oxides thereof.

9. Catalytically activated diesel particulate filter according to claim 1, characterized in that the filter body is selected from the group of filter substrates ceramic Wandfluß-, the Sintermetallfϊlterkörper or the ceramic or metallic foam structures.

10. Catalytically has activated diesel particulate filter according to claim 9, characterized in that the filter body is selected from the group of the ceramic wall flow filter substrates and walls having an open pore structure with a porosity of 40 to 80% and an average pore diameter of 9-30 micrometers.

11. Catalytically activated diesel particulate filter according to claim 1, characterized in that the filter body serves as a support body for the oxidation-active catalytic coating, wherein it occupies the entire length of the component, and characterized in that the oxidation-active, see katalyti coating the filter substrate provided as Tragköφer for catalytically active in the SCR reaction coating is used.

12. Catalytically activated diesel particulate filter according to claim 11, dadu rch i gekennze et chn, wherein the catalytically active in the SCR reaction occupies 5 to 50% coating of the length of the component and is arranged on the inflow side of the component.

13. Catalytically activated diesel particulate filter according to claim 10, dadu rch geke nnze i seframe that the oxidation-active catalytic coating is introduced over the entire length of the component into the pores of the walls of the ceramic wall flow filter substrate and distributed homogeneously in the particular wall of the Wandflußfϊltersubstrats.

14. Catalytically activated Dieselpartikelfϊlter according to claim 13, d adurc h geke nnze ic HNET that the oxidation-active catalytic coating to the upstream surface of the respective wall fills the pores in the walls of the ceramic wall flow filter substrate, and the catalytically active in the SCR reaction coating is applied to this surface.

15. Catalytically activated diesel particulate filter according to claim 14, d ad urch geke n nze i chn et that the active in the SCR reaction, catalytic coating occupies 5 to 50% of the length of the component and is arranged on the inflow side of the overall component.

16. Catalytically activated diesel particulate filter according to claim 13, d ABy g Eke n nze ichn et that the oxidation-active catalytic coating to the downstream surface of the respective wall fills the pores in the walls of the ceramic wall flow filter substrate, and the catalytically active in the SCR reaction coating also is incorporated into the pores of the walls and is distributed homogeneously in the particular wall but fills the pores up to the inflow-side surface of the respective wall.

17 exhaust gas purification system for removing nitrogen oxides and particulates from the exhaust gas of lean operating internal combustion engines, dad URC h geken nze i ch net that the exhaust gas cleaning system containing a suitable for removing nitrogen oxides catalyst and a catalytically activated diesel particulate filter according to one of claims 1 to 16 ,

18 exhaust gas purification system according to claim 17, d ad urch gekennze i seframe that the exhaust gas cleaning system on the upstream side of the catalytically activated diesel particulate filter includes means for metering ammonia or a compound decomposable to ammonia, and an SCR catalyst.

19 exhaust gas purification system according to claim 18, d ad URC h gekennze i Chne t that are disposed between the predominantly lean-operated internal combustion engine and the means for metering ammonia or a compound decomposable to ammonia, a diesel oxidation catalyst or a three way catalyst or a nitrogen oxide storage catalyst or combinations thereof.

20, exhaust gas purification system according to claim 17, characterized geke n nze i chn et that the emission control system includes, on the upstream side of the catalytically activated Dieselpartikelfϊlters a nitrogen oxide storage catalyst.